Currently, quantification of HIV-1 by viral load testing in resource-limited settings is performed in centralized laboratories by PCR-based methods using plasma samples. Dried blood spots have been employed as an alternative sample type, and while such alternatives may be beneficial for various reasons, the suitability of dried blood samples for viral load testing is questionable and depending on the assay used, proviral DNA and intracellular viral RNA present in dried blood spots interferes with RNA quantification.
In resource-limited settings or other field-based testing with unreliable or no access to phlebotomy or lab equipment, the collection and processing of plasma is challenging or impossible. Point of care testing is an alternative that has the potential to facilitate care for the greatest number of patients and point of care devices can be used to analyze whole blood samples easily collected using finger or heel prick and processing without additional instrumentation. However, there is a poor correlation in HIV viral loads measured by RT-PCR for whole blood samples vs. plasma. The T-cell subpopulation of white blood cells in whole blood has HIV proviral DNA, mRNA, and cell-associated virions. Hence, the quantification with whole blood is often higher than with plasma, especially at low titers. This can lead to what would otherwise be a viral load below the clinical threshold of 1e3 copies/ml to greater than 1e3 copies/ml. These results have been observed with fresh and frozen whole blood, as well as dried blood spots.
Because of the difficulties with collecting plasma samples in resource-limited settings, it is desirable to find a solution for a molecular point of care viral load test that gives quantitative results comparable to plasma.